How to make particle systems of particle systems?
I know of no way to be able to make a particle system with particle systems underneath.  However, there is a way you can convert the flower particles into mesh.  You have to start by applying any modifiers that are given to the objects being used in the particle systems applied to the flower.

Then you select the flower, go to the modifiers tab in the Properties bar, and click the convert button on each particle modifier.  The particles are now converted into a mesh.  Now join the petals, nectar stems, and sphere together so it's all one mesh.  Now you are able to make a particle system that uses this flower.

This does make the flower have more vertices, so you may want to go try to reduce the number of vertices to save memory.
Hope this helps